Refining mineral oils



Patented Nov. 1 7, 1942 name MINERAL OILS Henry G: Sclmtze, Baytown, Team, assignor to Standard Oil Development Company, a. corporation of Delaware No Drawings Application August 4, 1940, erial No. 351,437

6 Claims. (Cl. 196-30) The present invention relates to the refining of mineral oils and is especially concerned with the production of an improved quality oil which has been treated with copper-containing reagents for the removal or conversion of objectionable, sulfur compounds therefrom. In accordance with the present process, high quality stable petroleum oil products free of objectionable sulfur compounds are produced by treating a feed oil with a copper-containing reagent and then contacting the treated oil with an organic reagent capable of forming stable complex compounds with the copper atoms, thereby depriving the latter of their ability to catalyze deterioration of the oil while in storage.

It is well known in the art to remove sulfur compounds such as mercaptans from crude petroleum oils such as motor fuels, or to convert them into innocuous compounds by an appropriate chemical treatment, generally known as a sweetening operation. The chemical compound generally employed is a doctor solution which comprises a sodium plumbite solution made from a solution of caustic soda in which a definite amount of lead oxide is dissolved. The feed oil is treated with this solution under conditions to convert the mercaptans to the corresponding disulfides and the lead oxide then precipitated by the addition of free sulfur. An objection to this operation is that it is essential that the correct amount of sulfur be added necessary to completely precipitate the lead oxide. If excess sulfur be added it is dissolved in the gasoline and the treated product thus contains objectionable corrosive sulfur, necessitating rerunning or further treatment of the same. If an insuflicient quantity of sulfur be added, the treated product will contain dissolved lead oxide which is also very undesirable. Another objection to the doctor sweetening operation is that when addin the correct amount of sulfur the rate of reaction is relatively slow, particularly at the-point of equilibrium.

It has therefore been proposed to substitute other sweetening operations employing copper salts as well as salts of the other heavy metals such as mercury, for the purpose of removing objectionable sulfur compounds and converting them into harmless disulfides. A relatively wide- 1y used operation of this character comprises treating oils boiling in the motor fuel, kerosene, and Diesel fuel boiling range, with a reagent containing copper in the presence of a chloride, as for example ammonium chloride. This operation is not entirely satisfactory for the reason that although substantially the entire quantity of the copper salt is removed from the treated oil. the relatively small amount which is. difficult to remove apparently catalyzes subsequent deterioration of the treated oil. This is particularly the case when the 011 being treated contains various organic acids which react with the copper salts. In order to overcome this disadvantage, it has been proposed to further treat the oil, after removal of the copper solution, with a reagent having the ability to entirely free the oil of objectionable copper compounds. A known operation of this character comprises treating the copper-containing oil with an alkali or alkaline earth metal sulfide or carbonate solution.

I have now discovered a process by which sweetening operations utilizing reagents containing copper may be rendered particularly efiicient and economical, which will result in the production of a treated oil having a high stability against subsequent deterioration, and which is free of objectionable sulfur compounds. The process of my invention comprises treating a copper sweetened oil after removal of the copper treating solution with a relatively small quantity of an organic compound having a specific molecular structure. The compounds of my invention will react with the copper compound, which will removethe copper as the catalyzing agent. The compounds which are suitable for securing this result are selected from a wide class of materials which may be represented by the following structural formula:

in which R represents hydrogen an alkyl or aryl radical or may represent carbon or some other element which constitutes a member of a ring structure; in which C represents carbon or may boxyl group, or other acidic group; in which X represents nitrogen, oxygen, or sulfur contain- .ing at least one lone pair of electrons; and in which N represents a numeral from 0 to 2, inclusive. Compounds of this character. are for example, picolinic acid, quinolinic acid, o-aminophenol, m-aminophenol, anthranilic acid, glycine, ohydroxy-benzoic acid, o-carboxylic thiophenol, oxanilic acid, rubeanic acid, and o-amino-benzone sulfonic acid. Especially desirable substances comprise compounds which contain the following'linkage:

t t C-OOH as for example picolinic acid and quinoline-Z- as o-hydroxy-benzoic acid and o-carboxylic thiophenol. My compounds in general are characterized by the fact that there is a suilicient number of carbon atoms between the X and Y group so that upon reaction with the copper atom either five or six member ring compounds will be formed in the following manner:

k OJ

COOH' agent of the present invention be such that the resulting copper ring compound form be insoluble in the oil, and that the oil be filtered in order to remove these compounds.

The amount of the reagent used per volume of copper sweetened oil will vary considerably depending upon the type of the oil and the character of the copper ion present. If the copper ion is present in the oil in the cuprous state, ne mole oi! organic addition agent per mole of copper is necessary for complete reaction, whereas if the copper is present in the cupric state, two moles of inhibitor per mole of copper are required.

Temperature and pressure conditions may be adjusted in a manner adapted to secure a rapid rate of reaction. In general preferred temperature conditions are in the range from about 60 F. to 100 F. and preferred pressures are substantially atmospheric pressure.

In order to further illustrate the invention the following examplesare given which should not be construed as limiting the scope of the invention in any manner whatsoever:

ExAMPLs 1 Copper naphthenates were added to a hydrocarbon base oil which comprised an acid treated, redistilled and doctor sweetened cracked naphtha. The copper naphthenates were prepared by reacting naphthenic acids having a molecular weight of about 150 .with sodium hydroxide to form sodium naphthenates which were then reacted with copper sulfate to produce the copper naphthenates. Approximately 0.001 gram of copper naph'thenates per cubic centimeter of oil were dissolved in the base oil. Varying amounts of this oil solution were then added to larger volumes of an identical base oil in order to prepare the solutions appearing in Table I.

anthranilic acid was then dissolvedin pure benzene and the following operations conducted. Three one-gallon samples of the base oil were prepared for storage tests. The initial testutilized a base naphtha to which had been added 5.3 parts per million of copper in the form of copper naphthenates.

The second test utilized a base naphtha to which had been added 5.3 parts per million of.

inspection and the precipitant was not disturbed.

A third operation was conducted in the same manner identical with that of the second operation except that the insoluble complex copper anthranilatewas removed from the oil immedi-' ately by percolating the oil through a bed of unburned clay. The inspections on the oil from the respective operations, after various periods of storage, were as follows:

Table I Storage Saybolt res 0p. I down period color time Minutes 1 Base naphtha plus 5.3 3-day 26 405 P. P. M. copper. 2-week... 22 255 4-week 20 240 8-week.... 15 200 12-week... 16 210 16-week... 16 240 20-week... 16 260 2 Base naphtha plus 5.3 3-day 30 360 P. M. copper plus 2-week.... 30 250 32.16 P. P. M. anthra- 4-week... 30 360 nilic acid. Precipitate 8-week.... 27 360 not removed. 12-week... 26 300 16-week... 24 270 v i 20-week... 21 360 3 Base naphtha plus 5.3 3-day 30 230 P. P. M. copper plus 2-week.... 30 225 32.16 P. P. M. anthra- -i-week.... 30 265 nilic acid. Precipitate 8-week...- 30 205 removed by clay per- 12-week.-. 30 225 colation. 16-week. 30 180 20-week... 30 270 1 Test described in Ind. Eng. Chem., vol. 11, page 511 (1933).

From the above it is apparent that the addition of anthranilic acid to a base oil effects a marked improvement in its color stability and in its resistance to the breakdown oxidation itself. It is also to be noted that the oil percolated through clay for removal of the insoluble copper anthranilate complex had an unusually good color stability but had a poor resistance to the breakdown test. The low breakdown characteristic of the clay percolated oil, as confirmed by the following data on base oils free of added constituents, is believed to be due to some phenomena associated with the clay:

Table II Break- Storagc Saybolt Sample period color 2 Minutes Base naphtha percolated through 3-day... 30 clay; 2-week. 30 180 4-week. 30 240 8-week.... 30 12-week 30 180 16-week.-- 30 20-week... 30 115 Base naphtha not percolated 3-day.. 30 400 through clay. 2-week. 30 330 4-week... 2'7 360 8-week... 28 395 12-week... 29 16-week... 30 480 20-week... 29 360 EXAMPLE 2 In another series of tests the copper naphthenates employed in Example 1 were utilized. However, the organic addition agent comprised crystalline anthranilic acid an one operation and a solution of anthranilic acid in isopropyl alcohol in other operations. In these operations five one-gallon samples of naptha were prepared for tered through two thicknesses of filter paper to.

remove the insoluble copper anthranilate complex before placing in storage. A third sample consisted of base naphtha to which had been added 2.65 P. P. M. of copper and 16.08 P. P. M.

of anthranilic acid dissolved in isopropyl alcohol (0.7 cc. per gallon of oil sample). This sample was settled for three hours and then filtered through filter paper to remove the insoluble copper anthranilate complex before placing the sample in storage. A fourth sample consisted of base naphtha to which had been added 2.65

P. P. M. of copper as copper naphthenate and 11.45 P. P. M. of anthranilic acid dissolved in isopropyl alcohol, the alcohol used being equivalent to 0.5 cc. per gallon of 011 sample. This sample was settled for a period of 3.5 hours before filtering to remove the insoluble copper anthranilate complex. The 11.45 P. P. M. of an- While this invention has been described with specific reference to the conversion of copper atoms present in oil to stable complex compounds so as to render them incapable of promoting deterioration of the oil while in storage, the process may also be employed for conversion of the atoms of other metals, such as cobalt, nickel, chromium, zinc, silver and cadmium to stable complex compounds for the same purpose.

The process of the present invention is not to be limited by any theory or mode of operation but only by the following claims in which it is desired to claim all novelty insofar as the prior art permits. I claim:

1. The process of stabilizing petroleum 011' which has been sweetened with a copper containing reagent, which comprises treating said 011- with anthranilic acid to precipitate an insoluble complex copper-containing compound from retained copper salts reacted with said anthranilic acid, and separating said precipitate from the oil.

. 2. The process as defined by claim 1 in which said petroleum oil comprises an oil boiling in the motor fuel-boiling range.

thranilic acid is the amount just equivalent to I 2.65 P. P. M. of copper as copper naphthenates, whereas 16.08 P. P. M. of the acid amounted to a 40% excess over that equivalent to the copper. A fifth sample, prepared as a control, consisted of base naphtha in which had been dissolved 0.7 cc. of isopropyl alcohol per gallon of sample.

The storage data on the respective samples are tabulated below: I

Table III Break- Storage Saybolt Sample period color 13::

Minutes Base naphtha plus 2.65 P. P. M. May"... 21 240 copper. 2-week 20 360+ 4-week..-. 16 270 8-week... 4 325 12-week..- 0 240 lit-week--- j 3 316 20-wee 6 135 Base naphtha plus 0.7 cc. iso- 3-day...-. 26 285 propyl alcohol per gallon. 2-week 24 360+ 4-week 23 360 8-week..-. 21 810 12-week... 21 240 iii-week..- 21 480 20-week--. 20 360 Base naphtha plus 2.65 P. P. M. 3-dey. 26 465 copper plus 16.08 P. P. M. 2-week.... 360+ crystalline anthranllic acid. 4-week.. 30 360+ Precipitate removed by filtra- 8-week.... 20 360+ tlon. 12-week.-- 28 480 lit-wee 28 106 20-wee 26 360 Base naphtha plus 2.66 P. P. M. 6-day.-... 26 316 cop r lus 16.08 P. P. M. 2-week.... 28 345 out ic acid in isopropyl 4-week 29 360+ alcohol. Precipitate removed 8-week.... 20 360+ by filtration. 12-week. 30 360+ lit-week..- 30 315 20-week.-- 30 830 Due naphtha plus 2.66 P. P. M. 3-day. 26 315 cop r In: 11.45 P. P. M 2-week.... 26 380 ant c acid in isopropyl 4-week.... 27 360+ alcohol. Precipitate removed 8-week. 28 360+ by filtration. 12-week. 26 860+ lav-week.-- 26 285 20-week... 21 360 The above data show that the addition of anthranilic acid to a copper-bearing oil, followed by its filtration through a suitable filter for removal of. the resultant insoluble complex copper compound, is an effective method for rendering such oil stable against deterioration while in storage.

3. In the process of sweetening a hydrocarbon oil with a copper reagent, the step of stabilizing the sweetened oil to prevent deterioration thereof caused by copper remaining in the sweetened oil, which comprises reacting with said retained copper in the sweetened 011 an organic aminoacid to form a stable complex containing the copper in a 5 to 6 membered ring, said aminoacid being characterized by having the nitrogen atom of an amino group linked to the carbon atom of a carboxyl group thru one to two inter vening carbon atoms.

4. In a process of sweetening a petroleum oil with copper reagents, the step of stabilizing the sweetened oil to prevent deterioration due to retained oil-soluble copper salts, which comprises adding to said sweetened oil a small quantity of an aromatic amino carboxylic acid in which a trivalent nitrogen constituent of an amino group is linked by a series of 1 to 2 carbon atoms to the carbon constituent of a carboxyl group so that upon reaction of the arc-- matic amino carboxylic acid with the copper salt, copper is substituted for a hydrogen atom in the carboxyl group and becomes bonded to the nitrogen in the amino group as a constituentof a 5 to 6 membered ring in combination with said aromatic amino acid.

5. The method of stabilizing a hydrocarbon oil treated with a copper salt reagent to prevent deterioration caused by retained oil-soluble copper salts, which comprises reacting said copper salts with an aromatic amino acid wherein trivalent nitrogen of an amino group is linked to the carbon atom of a carboxylic radical through 1 to 2 carbon atoms.

6. The method of stabilizing a hydrocarbon oil to prevent deterioration normally induced by a copper compound left in the oil in sweetening by a copper reagent, which comprises combining copper from said compound into a complex compound with an aromatic aminoacid wherein nitrogen of an amino groupand carbon of a carboxyl radical are located in ortho positions.

HENRY G. SCHUTZE. 

